My Son, the Chimp. S1E28

Uncle Fester thinks his conjuring mishap has turned Pugsley into a chimpanzee. The family is unaware that Fester's explosion merely knocked Pugsley into a secret room, where he's trapped. The chimpanzee is a real chimpanzee that escaped from an organ grinder and climbed into Pugsley's window. Pugsley befriended the animal outside anyone's notice and the chimpanzee dressed itself in a duplicate set of his clothes. Fester keeps trying but can't seem to turn the chimpanzee back into Pugsley. In the end, Fester accidentally frees Pugsley and gets himself trapped in the secret room. Fivel and JohnPaul also chat about comic books, Trash Pack toys, Detectives, New York City movies, and how bad JohnPaul is at primates.